The present invention is directed generally to ophthalmic lenses, and more particularly, to intraocular lenses having aspherical profiles.
Generally speaking, asphericity describes the extent to which a curved, three-dimensional surface deviates from an ideal spherical shape. In the case of a lens, the asphericity can manifest itself on the anterior surface, the posterior surface or in the combined effect of both surfaces as they refract light passing through the lens.
The principal optical components of the natural eye are the cornea, which forms the anterior of the eye, and the natural crystalline lens that lies within the eye. The cornea is the first component of the ocular system and provides roughly two-thirds of the focusing power of the system. The crystalline lens provides the remaining focusing capability of the eye.
An intraocular lens (IOL) is typically implanted in a patient's eye during cataract surgery to compensate for the lost optical power when the natural lens is removed. In many cases, however, the optical performance of the IOL may be degraded by inherent corneal aberrations. The human cornea generally exhibits a positive spherical aberration, which is typically offset by a negative spherical aberration of the natural crystalline lens. If this positive spherical aberration of the cornea is not accounted for, it will adversely affect the focusing of light by the combined system of cornea and an implanted IOL.
Intraocular lenses that compensate for spherical aberration are known. However, there is no consensus on how, or the extent to which, an IOL should compensate for the corneal aberration. Accordingly, there is a need for improved ophthalmic lenses, and particularly, for improved IOLs that address the issue of spherical aberration.